A vehicular seat belt device is known in which the restraint of an occupant by a webbing is enhanced by winding up the webbing with an actuator during an emergency. This seat belt device is provided with: a gas generator that instantaneously generates a high-pressure gas upon receiving an input of an actuation signal; and an actuator that causes a belt reel to rotate upon receiving a gas pressure that is generated by the gas generator. When the gas generator generates a high-pressure gas during an emergency, the webbing is instantaneously drawn in by the actuator that has received that gas pressure.
However, in the case of this type of seat belt device, since the large drive force that is obtained by the gas generator is of an instantaneous nature, it is difficult to sustain the restraining force of the occupant by the webbing.
For this reason, to counter this a constitution has been proposed that couples a flywheel to a rotation axis of the actuator that uses gas pressure, whereby it is possible to sustain the restraining force by the inertial rotation of the flywheel after the gas pressure rapidly falls (refer to, for example, Patent Document 1).
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2003-25955